Fuel injection valve for internal combustion engines, and a method for producing same

ABSTRACT

A fuel injection valve having a valve retaining body, which has a longitudinal axis and in which a central spring chamber is embodied. In this spring chamber, a closing spring is disposed, which transmits a closing force to a valve member, which valve member cooperates with a valve seat for controlling at least one injection opening. In the wall of the spring chamber, an inlet conduit extends parallel to the longitudinal axis of the valve retaining body, and by way of this conduit, fuel at high pressure can be delivered to the at least one injection opening. The cross section of the inlet conduit has a greater length in the circumferential direction than in the radial direction, so that the wall region between the inlet conduit and the spring chamber, or the outer jacket face of the valve retaining body, is larger than in the case of an inlet conduit with the same size of cross-sectional area and a circular cross-sectional contour.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 application of PCT/DE 00/04586 filed onDec. 22, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is based on a fuel injection valve for internal combustionengines.

2. Description of the Prior Art

In one such fuel injection valve, known from German Published,Nonexamined Patent Application DE 196 08 575 A1, a valve body is axiallybraced against a valve retaining body with a tightening nut, with theinterposition of a shim. In the valve body, a bore is embodied, in whicha pistonlike valve member is disposed that is axially movable counter toa closing force. On the end of the valve member toward the combustionchamber, a valve sealing face is embodied on the valve member; this facecooperates with a valve seat embodied on the end toward the combustionchamber of the bore, so that the valve member, as a result of an openingstroke motion counter to a closing force, opens at least one injectionopening. An inlet bore is embodied in the valve retaining body, shim andvalve body, and through this bore fuel at high pressure reaches as faras the valve seat and, when the fuel injection valve is opened, isinjected through the injection openings into the combustion chamber ofan internal combustion engine.

A hollow chamber is embodied centrally in the valve retaining body, anda prestressed spring is disposed in the hollow chamber. The spring isbraced, toward the combustion chamber, on a valve plate joined to thevalve member and thus generates the closing force on the valve member.The inlet conduit extends in the wall of the spring chamber and parallelto it. The result, in the known fuel injection valves, is thedisadvantage that if the valve retaining body has a slender design, thewall of the inlet conduit must not drop below a certain wall thickness,if it is to be able to withstand the fuel pressure. Hence there is alimit to making the valve retaining body any slenderer or increasing thefuel pressure in the inlet conduit, and with the construction known thusfar it has not been possible to go below this limit.

SUMMARY OF THE INVENTION

The fuel injection valve of the invention having the definitivecharacteristics of claim 1 has the advantage over the prior art that theinlet conduit in cross section has an oval or elliptical shape, and thegreatest length, or major axis, points in the circumferential directionof the valve body part. As a result, the wall region between the hollowchamber and the inlet conduit, or between the inlet conduit and theouter wall face of the valve body part, is larger without there being aneed to reduce the cross-sectional area of the inlet conduit. As aresult, for the same outside dimensions of the valve body part and thesame embodiment of the hollow chamber, a higher fuel pressure in theinlet conduit of the valve body part can be achieved. Alternatively,provision can be also made to give the valve body part a slendererdesign, and to leave the fuel pressure in the inlet conduit unchanged.

An inlet conduit of oval cross section offers the advantage over acircular cross section that because of the greater wall thicknessbetween the inlet conduit and the hollow chamber, or between the inletconduit and the outer jacket face of the valve body part, greatertolerance in the manufacture of the valve body part is permissible,without any loss of stability to resist the high fuel pressure in theinlet conduit. As a result, the valve body part can be produced at lesseffort and thus less expense.

In an advantageous method for producing the fuel injection valve of theinvention, a circular bore is made eccentrically in a cylindrical body,which body is solid and preferably is of metal, the bore being parallelto the longitudinal axis of this body. The cylindrical body has an outerdiameter that is greater than the desired outer diameter of the valvebody part. By plastic deformation of the cylindrical body, the desiredouter diameter is achieved while maintaining the cylindrical shape ofthe outer jacket face; the cross section of the inlet conduit isdeformed and assumes an oval or elliptical shape. Only after this methodstep is the hollow chamber formed, so that the inlet conduit extendswithin the wall of the hollow chamber. By means of this method it isadvantageously possible to produce an inlet conduit of oval orapproximately elliptical cross section, without embodying such an inletconduit directly in the valve body part, such as by drilling or milling,which would be complicated and hence expensive.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent from thedescription contained below taken with the drawings, in which:

FIG. 1 shows a longitudinal section through a fuel injection valve ofthe invention, and

FIG. 2 shows a cross section through the fuel injection valve, shown inFIG. 1, at the level of the spring chamber along the line II—II.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, a longitudinal section through a fuel injection valve of theinvention is shown. The fuel injection valve has a valve body 20, whichis braced with a tightening nut 22, with the interposition of a shim 15,against a valve body part embodied as a valve retaining body 1. In thevalve body 20, a bore 25 is embodied as a blind bore, and on its endtoward the combustion chamber, there is a substantially conical valveseat 32, in which at least one injection opening 36 is disposed. Apistonlike valve member 30 is disposed in the bore 25; the valve memberis guided in the bore 25 in a portion remote from the combustion chamberand narrows, forming a pressure shoulder 28, toward the combustionchamber. On the end toward the combustion chamber of the valve member30, a substantially conical valve sealing face 34 is formed, whichcooperates with the valve seat 32 to control the at least one injectionopening 36. The pressure shoulder 28 is disposed in a pressure chamber27 embodied in the valve body 20, and this pressure chamber continues,in the form of an annular conduit surrounding the valve member 30, asfar as the valve seat 32. On the end of the valve member 30 remote fromthe combustion chamber, the valve member is connected to a spring plate31, which is disposed in an opening in the shim 15 and protrudes as faras the inside of a central hollow chamber, embodied as a spring chamber5, in the valve retaining body 1. The spring chamber 5 is embodied as acentral bore 8 in the valve retaining body 1 and is disposed at leastapproximately coaxially to the bore 25. A device embodied as a closingspring 6 is disposed in the spring chamber 5; this closing spring 6 isprestressed and is braced toward the combustion chamber on the springplate 31 and remote from the combustion chamber on the bottom face,remote from the combustion chamber, of the spring chamber 5. Because ofthe prestressing of the closing spring 6, a closing force is exerted onthe valve member 30, with which the valve member is pressed by the valvesealing face 34 against the valve seat 32. An outlet conduit 10discharges into the bottom face, remote from the combustion chamber, ofthe spring chamber 5, and by way of this conduit the leaking oil,flowing out of the pressure chamber 27 past the guided portion of thevalve member 30 into the spring chamber 5 can flow away.

The pressure chamber can be filled with fuel at high pressure via aninlet conduit 3 extending within the valve retaining body 1, shim 15 andvalve body 20. The end of the inlet conduit 3 opposite the pressurechamber 27 discharges into a high-pressure connection 12, which isdisposed on the face end, remote from the combustion chamber, of thevalve retaining body 1, approximately in the longitudinal axis 2 of thevalve retaining body 1, and which communicates with a high-pressure fuelsystem, not shown in the drawing. From the high-pressure connection 12,the inlet conduit 3 leads, inclined at an angle to the longitudinal axis2 of the valve retaining body 1, as far as an intersection 4. From theintersection 4, the inlet conduit 3 extends at least approximatelyparallel to the longitudinal axis 2 of the valve retaining body 1 in thewall of the spring chamber 5, as far as the shim 15. In the shim 15 andin the valve body 20, the inlet conduit 3 again extends at an incline tothe longitudinal axis 2 of the valve retaining body 1 and intersects thepressure chamber 27 at the level of the pressure shoulder 28 of thevalve member 30. A fuel filter 18, which filters troublesome particlesout of the inflowing fuel, may be provided in the inlet conduit 3between the high-pressure connection 12 and the kink 4.

In FIG. 2, a cross section through the fuel injection valve shown inFIG. 1 is shown, at the level of the spring chamber 5. In FIG. 2, theclosing spring 6 is not shown, for the sake of simplicity. The inletconduit 3 in cross section has a greater length in the circumferentialdirection of the valve retaining body 1 than in the at leastapproximately radial direction, and for instance as shown in FIG. 2 hasan oval, approximately elliptical cross section. As a result, the wallthickness between the inlet conduit 3 and the spring chamber 5, orbetween the inlet conduit 3 and the outer jacket face of the valveretaining body 1, is embodied as greater than in an inlet conduit 3 ofcircular cross section and the same size of cross-sectional area. Asalternative to the cross section shown in FIG. 2, it can also beprovided that the inlet conduit 3 has a different cross-sectional shape.However, the orientation of the inlet conduit 3 is always such that thegreatest length of the cross section of the inlet conduit points in thecircumferential direction of the valve retaining body 1.

The function of the fuel injection valve is as follows: Via the inletconduit 3, fuel at high pressure is pumped into the pressure chamber 27.Because of the fuel pressure, a hydraulic force is exerted on thepressure shoulder 28 of the valve member 30. If the component of thishydraulic force acting in the axial direction exceeds the force of theclosing spring 6, then the valve member 30 with the valve sealing face34 lifts up from the valve seat 32, until it comes into contact with astop face embodied in the shim 15. By this opening stroke motion of thevalve member 30, the injection opening 36 is made to communicate withthe pressure chamber 27, and fuel is injected into the combustionchamber of the engine. The end of the injection event is initiated byproviding that the fuel pressure in the inlet conduit 3, and thus alsoin the pressure chamber 27, drops. As a result, the hydraulic force onthe pressure shoulder 28 of the valve member 30 decreases, until itsaxial component becomes less than the force of the closing spring 6. Thevalve member 30 is now accelerated again in the direction of the valveseat 32 by the force of the closing spring 6, until the valve member 30with the valve sealing face 34 comes to rest on the valve seat 32 andthus closes the injection opening 36.

As an alternative to the closing spring 6 shown in FIG. 1, it can alsobe provided that the closing force on the valve member 30 is exerted bysome other device, such as a hydraulic or magnetic device. It can alsobe provided that instead of the spring chamber 5, a central opening isembodied, in which a mechanical element is disposed that transmits theclosing force to the valve member 30. Furthermore, instead of the valvebody 20 shown in the drawing, it is possible to use other suitable valvemembers, such as valve members that open outward. The inlet conduit 3 ofthe invention can be realized not only in the fuel injection valve shownbut also in any other valve retaining body 1 which has a central hollowchamber and an inlet conduit that extends in the wall of this hollowchamber.

The fuel inlet conduit of the invention can advantageously be producedby the following method. A bore which has a circular cross section ismade eccentrically to a cylindrical body, which is solid and preferablycomprises metal, the bore being at least approximately parallel to thelongitudinal axis of the cylindrical body. The cylindrical body has anouter diameter that is greater than the predetermined value of the valveretaining body 1 to be produced. By mechanical machining, thecylindrical body is then plastically deformed, so that while maintainingits cylindrical shape of the outer jacket face, it is reduced indiameter, until the predetermined value of the valve retaining body 1 tobe produced is attained. As a result, the cross section of the inletconduit 3 changes as well and assumes an oval to ellipticalcross-sectional contour. After this deformation, a central hollowchamber forming the spring chamber 5 is embodied in the valve retainingbody 1, so that the inlet conduit 3 extends in the wall of the springchamber 5. After that, all the other characteristics of the valveretaining body 1 can be embodied in a conventional way. The plasticdeformation of the cylindrical body is advantageously done by rolling ofthe cylindrical body, making a permanent plastic reshaping of thecylindrical body possible while maintaining its cylindrical shape of theouter jacket face. As an alternative to rolling, some other suitabledeforming method can also be selected. The foregoing relates topreferred exemplary embodiment in the invention, it being understoodthat other variants and embodiments thereof are possible within thespirit and scope of the invention, the latter being defined by theappended claims.

1. A fuel injection valve for internal combustion engines comprising avalve body part (1) having a longitudinal axis and in which a centralhollow chamber (5) is embodied, means (6) disposed in said hollowchamber (5) that transmits a force to a valve member (30), and an inletconduit (3), which extends in the wall of the central hollow chamber (5)parallel to the longitudinal axis (2) of the valve body part (1), and byway of which inlet conduit (3), fuel at high pressure can be deliveredto at least one injection opening (36), said inlet conduit (3) in thecircumferential direction having a greater length than in an at leastapproximately radial direction.
 2. The fuel injection valve of claim 1,wherein said inlet conduit (3) has an at least approximately oval crosssection.
 3. The fuel injection valve of claim 2, wherein the two pointsof the oval cross section located farthest apart from one another in theinlet conduit (3) have at least approximately the same spacing from thelongitudinal axis (2) of the valve body (1).
 4. The fuel injection valveof claim 2, wherein said oval cross section of the inlet conduit (3) atleast approximately forms an ellipse.
 5. A method for producing a valvebody part (1) of a fuel injection valve of claim 1, comprising the stepsof in an at least approximately cylindrical body, a bore forming theinlet conduit (3) is embodied eccentrically and at least approximatelyparallel to the longitudinal axis (2) of said conduit; reducing thediameter of the body, while maintaining its at least approximatelycylindrical shape, by plastic deformation, until a predetermineddiameter is attained, and the cross section of the bore is changed insuch a way that the cross section has a greater length in thecircumferential direction than in the at least approximately radialdirection; and forming the central hollow chamber (5) in the body sothat the inlet conduit (3) extends in the wall of the central hollowchamber (5).
 6. The method of claim 5, wherein said body forming thevalve body part (1) is of metal, preferably steel.
 7. The method ofclaim 6, wherein the steps of plastic deformation of the cylindricalmetal body is accomplished by rolling.